package org.rockyang.blockj.base.utils;

import org.rockyang.blockj.base.exceptions.MessageDecodingException;
import org.rockyang.blockj.base.exceptions.MessageEncodingException;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Arrays;

/**
 * <p>Message codec functions.</p>
 *
 * <p>Implementation as per https://github.com/ethereum/wiki/wiki/JSON-RPC#hex-value-encoding</p>
 */
public final class Numeric {

	public static final String HEX_PREFIX = "0x";

	private Numeric()
	{
	}

	public static String encodeQuantity(BigInteger value)
	{
		if (value.signum() != -1) {
			return HEX_PREFIX + value.toString(16);
		} else {
			throw new MessageEncodingException("Negative values are not supported");
		}
	}

	public static BigInteger decodeQuantity(String value)
	{
		if (!isValidHexQuantity(value)) {
			throw new MessageDecodingException("Value must be in format 0x[1-9]+[0-9]* or 0x0");
		}
		try {
			return new BigInteger(value.substring(2), 16);
		} catch (NumberFormatException e) {
			throw new MessageDecodingException("Negative ", e);
		}
	}

	private static boolean isValidHexQuantity(String value)
	{
		if (value == null) {
			return false;
		}

		if (value.length() < 3) {
			return false;
		}

		if (!value.startsWith(HEX_PREFIX)) {
			return false;
		}

		// If TestRpc resolves the following issue, we can reinstate this code
		// https://github.com/ethereumjs/testrpc/issues/220
		// if (value.length() > 3 && value.charAt(2) == '0') {
		//    return false;
		// }

		return true;
	}

	public static String cleanHexPrefix(String input)
	{
		if (containsHexPrefix(input)) {
			return input.substring(2);
		} else {
			return input;
		}
	}

	public static String prependHexPrefix(String input)
	{
		if (!containsHexPrefix(input)) {
			return HEX_PREFIX + input;
		} else {
			return input;
		}
	}

	public static boolean containsHexPrefix(String input)
	{
		return !Strings.isEmpty(input) && input.length() > 1
				&& input.charAt(0) == '0' && input.charAt(1) == 'x';
	}

	public static BigInteger toBigInt(byte[] value, int offset, int length)
	{
		return toBigInt((Arrays.copyOfRange(value, offset, offset + length)));
	}

	public static BigInteger toBigInt(byte[] value)
	{
		return new BigInteger(1, value);
	}

	public static BigInteger toBigInt(String hexValue)
	{
		String cleanValue = cleanHexPrefix(hexValue);
		return toBigIntNoPrefix(cleanValue);
	}

	public static BigInteger toBigIntNoPrefix(String hexValue)
	{
		return new BigInteger(hexValue, 16);
	}

	public static String toHexStringWithPrefix(BigInteger value)
	{
		return HEX_PREFIX + value.toString(16);
	}

	public static String toHexStringNoPrefix(BigInteger value)
	{
		return value.toString(16);
	}

	public static String toHexStringNoPrefix(byte[] input)
	{
		return toHexString(input, 0, input.length, false);
	}

	public static String toHexStringWithPrefixZeroPadded(BigInteger value, int size)
	{
		return toHexStringZeroPadded(value, size, true);
	}

	public static String toHexStringWithPrefixSafe(BigInteger value)
	{
		String result = toHexStringNoPrefix(value);
		if (result.length() < 2) {
			result = Strings.zeros(1) + result;
		}
		return HEX_PREFIX + result;
	}

	public static String toHexStringNoPrefixZeroPadded(BigInteger value, int size)
	{
		return toHexStringZeroPadded(value, size, false);
	}

	private static String toHexStringZeroPadded(BigInteger value, int size, boolean withPrefix)
	{
		String result = toHexStringNoPrefix(value);

		int length = result.length();
		if (length > size) {
			throw new UnsupportedOperationException(
					"Value " + result + "is larger then length " + size);
		} else if (value.signum() < 0) {
			throw new UnsupportedOperationException("Value cannot be negative");
		}

		if (length < size) {
			result = Strings.zeros(size - length) + result;
		}

		if (withPrefix) {
			return HEX_PREFIX + result;
		} else {
			return result;
		}
	}

	public static byte[] toBytesPadded(BigInteger value, int length)
	{
		byte[] result = new byte[length];
		byte[] bytes = value.toByteArray();

		int bytesLength;
		int srcOffset;
		if (bytes[0] == 0) {
			bytesLength = bytes.length - 1;
			srcOffset = 1;
		} else {
			bytesLength = bytes.length;
			srcOffset = 0;
		}

		if (bytesLength > length) {
			throw new RuntimeException("Input is too large to put in byte array of size " + length);
		}

		int destOffset = length - bytesLength;
		System.arraycopy(bytes, srcOffset, result, destOffset, bytesLength);
		return result;
	}

	public static byte[] hexStringToByteArray(String input)
	{
		String cleanInput = cleanHexPrefix(input);

		int len = cleanInput.length();

		if (len == 0) {
			return new byte[]{};
		}

		byte[] data;
		int startIdx;
		if (len % 2 != 0) {
			data = new byte[(len / 2) + 1];
			data[0] = (byte) Character.digit(cleanInput.charAt(0), 16);
			startIdx = 1;
		} else {
			data = new byte[len / 2];
			startIdx = 0;
		}

		for (int i = startIdx; i < len; i += 2) {
			data[(i + 1) / 2] = (byte) ((Character.digit(cleanInput.charAt(i), 16) << 4)
					+ Character.digit(cleanInput.charAt(i + 1), 16));
		}
		return data;
	}

	public static String toHexString(byte[] input, int offset, int length, boolean withPrefix)
	{
		StringBuilder stringBuilder = new StringBuilder();
		if (withPrefix) {
			stringBuilder.append("0x");
		}
		for (int i = offset; i < offset + length; i++) {
			stringBuilder.append(String.format("%02x", input[i] & 0xFF));
		}

		return stringBuilder.toString();
	}

	public static String toHexString(byte[] input)
	{
		return toHexString(input, 0, input.length, false);
	}

	public static byte asByte(int m, int n)
	{
		return (byte) ((m << 4) | n);
	}

	public static boolean isIntegerValue(BigDecimal value)
	{
		return value.signum() == 0
				|| value.scale() <= 0
				|| value.stripTrailingZeros().scale() <= 0;
	}
}
